Unconditionally secure polarization based Quantum Key Distribution with laser pulses implementations
Kiyoshi Tamaki, Hoi‐Kwong Lo · arXiv (Cornell University) · 2004
We prove the unconditional security of ``Quantum cryptography protocols robust against photon number splitting attacks for weak laser pulses implementations'' proposed by V. Scarani {\\it et al.,} in Phys. Rev. Lett. {\\bf 92}, 057901 (2004), which is called SARG04. Since a perfect single-photon source is not available with current technologies, many of experiments for quantum key distribution rely on attenuated coherent sources. It has been suggested that we can generate a secret key not only from single-photon emission parts, but also two-photon emission parts in SARG04. Our security analysis shows that we can indeed generate an uncondtionally secure key from two-photon part when the bit error rate on the part is below about 2.71% regardless of channel losses. Our analysis can be applied to $N$-state protocol with two-photon parts, and also may be applied to the less than $(N-1)$-photon parts.